Implantable device

ABSTRACT

An implantable device for aiding in generating connective tissue between a pair of anatomical structures in a mammalian body is provided. The device includes an elongate, flexible tether which can be secured between the anatomical structures and which carries a scaffold which is generally porous so as to be capable of promoting tissue ingrowth and collagen deposition along its length. The scaffold extends along the tether for a sufficient distance so that it is securable in at least close proximity to an anatomical structure at either end. The pores in the scaffold extend through the scaffold and each has a diameter in the range of about 10 μm to about 200 μm. The length of the tether is selected to be a desirable maximum distance between the anatomical structures along a desired path when secured therebetween.

FIELD OF THE INVENTION

This invention relates to an implantable device and method for usingsuch a device. One aspect of the invention provides for an implantabledevice which may be useful in the treatment of conditions relating tosleep apnoea.

BACKGROUND TO THE INVENTION

Obstructive sleep apnoea (OSA) is a serious, debilitating conditioncharacterised by blockage of the upper airway during sleep as a resultof collapse of the soft tissues in the throat. OSA is associated withsignificant morbidity and mortality, the impact of which has not as yetbeen fully defined and assessed in the global community. It is estimatedthat approximately 2% to 4% of the adult population in Western countriesare affected, but these figures may represent a gross under-estimationof the problem. Patients suffering from OSA have sleep fragmentation anddeprivation as they are unable to achieve adequate rapid eye movementsleep resulting in a non-refreshing sleep pattern. The major symptom ofOSA is excessive daytime sleepiness (EDS). As a result, lack ofconcentration and memory, changes in mood and personality as well as anincrease in workplace and traffic accidents have been linked to EDS.Moreover, there are significant comorbidities linked to OSA. Theseinclude cardiovascular, cerebrovascular, endocrine/metaboliccomplications and premature death.

There exists a strong relationship between obesity and OSA. It has beenreported that 60-90% of patients suffering from OSA have a body massindex (BMI) 30 Kg/m². In 1997, the World Health Organization formallyrecognized the global nature of obesity and declared it an epidemic. Asthe prevalence of obesity increases there is likely to be a parallelincrease in OSA. In the adult population, the prevalence of OSA isestimated at 25%, rising to 45% in obese individuals. While OSA is morecommon in men and in the elderly age group, it can also occur inchildren and young adults. Obesity in children and young adults isreaching epidemic proportions. Obese children have a 46% prevalence ofOSA compared to children seen in a general paediatric clinic (33%). Therisk of children and adolescents with OSA to develop metabolic syndromeis six fold greater than their counterparts without OSA. Obesity isconsidered a major risk factor in the development and progression ofOSA. In obese and severely obese individuals, the prevalence of OSA isnearly twice that of normal BMI adults.

Moreover, a 10% weight gain in patients with mild OSA can increase theirrisk by 6 times to progress to severe OSA while an equivalent weightloss can result in a 20% improvement of OSA severity.

The upper airway in humans is the space between the nasal cavity and thelarynx. Within this space lies the pharynx which is germane to airflowinto the lungs and where the collapse takes place. The pharynx has threeanatomical levels. The nasopharynx begins at the back of the nasalcavity and forms the uppermost portion of the pharynx. The oropharynx isthe intermediate portion which contains the soft palate, uvula, base oftongue and epiglottis. Due to the high presence of soft tissuestructures in the oropharynx it is the most likely anatomical part toobstruct and collapse. The hypopharynx is the area behind and below theopening of the larynx and extends into the oesophagus.

It is well known that the soft palate and tongue are both flexiblestructures with the soft palate providing a barrier between the nasalcavity and the mouth. In OSA the soft palate often hangs down betweenthe tongue base and posterior pharyngeal wall. During sleep most musclesof the body relax while those of the respiratory system remain active.In particular, the diaphragm contracts and pushes the abdominal contentsdownwards in order to create a negative pressure within the chest cage.Air is thus sucked in through the nasal and oral cavities into the lungsthrough the pharynx. The negative pressure of inhalation is usuallycounteracted by the compliance of the pharyngeal wall. In patients withOSA the soft palate, tongue and/or epiglottis collapse against theposterior pharyngeal wall and block airflow into the trachea. As theairway becomes narrow turbulence in the pharynx causes the soft palateto vibrate thereby generating the sound of snoring.

It is possible that due to the deposition of fat at specific anatomicsites, as seen in obese patients, OSA may be aggravated. Compliance ofthe upper airway is negatively affected by the external pressure ofpara-pharyngeal fat deposition. This results in a smaller lumen andincreased collapsibility of the pharynx, in so doing predisposing theindividual to OSA. In addition, deposits of fat around the thorax(truncal obesity) can reduce chest compliance and functional residualcapacity, thereby increasing oxygen demand. Visceral obesity is alsocommonly seen in OSA.

The consistency of the effect of body weight on the progression of thedisease process across different cohorts strongly suggests that manypatients with OSA present with a clinical history of recent weight gain.In view of the above and given the fact that obesity is reachingepidemic proportions, the close association between weight gain anddisease progression heightens the concern that OSA, with its attendantplethora of serious comorbidities, as well as attendant complications,will inevitably impose an enormous financial burden upon health caredelivery.

The basic epidemiological features of OSA are well established. Thediagnosis of OSA is dependent upon both subjective and objectiveappraisal. A comprehensive clinical and sleep history includes theevaluation of subjective symptoms such as habitual snoring, EDS,nocturnal witnessed apnoea and a physical examination. The gold standardfor the objective measurement of sleep disordered breathing (SDB)remains the polysomnogram (PSG) or sleep study. During sleep, it isoften the case that brief obstructions of airflow and/or small decreasesin the amount of airflow into the lungs can occur. An obstruction ofairflow for more than 10 seconds is referred to as an apnoea.

OSA is defined by the number of apnoea and hypopnoea episodes per hourof sleep (apnoea-hypopnoea index, AHI) reflecting the departure from thenormal physiology of breathing during sleep. Apnoeas are furtherclassified as obstructive, central, or mixed based on whether effort tobreathe is present during the event. A hypopnoea is defined as areduction in airflow that is followed by an arousal from sleep or adecrease in oxyhaemoglobin saturation. Commonly used definitions of ahypopnoea require a 25% or 50% reduction in oronasal airflow associatedwith either a reduction in oxyhaemoglobin saturation or an arousal fromsleep. The term “OSA syndrome” is used to indicate a clinical entitydefined by an elevated AHI (having 10 or more episodes of apnoea orhypopnea per hour of sleep) in conjunction with hypersomnolence orrelated problems in daytime function and is synonymous with the term“obstructive sleep apnoea-hypopnoea syndrome” (OSAHS).

CPAP or continuous positive airway pressure treatment remains the goldstandard for OSA because of its effectiveness in the elimination ofapnoea and improvements in its sequalae. It operates by delivering airinto the patient's airway through a specifically designed nasal mask orpillow. The inflow of air creates a positive pressure during inhalation,thereby maintaining an open airway and pushing and splinting the tonguebase in a forward direction. In this way compliance and patency ismaintained. Outcomes of randomised trials have shown substantialimprovements in both sleepiness and neurocognitive performance ofpatients on nasal CPAP compared with those on placebo or sub therapeuticCPAP. Moreover, improvements in blood pressure have been shown with CPAPtreatment. However, CPAP adherence is still difficult. Patency of theupper airway is germane to comfort and successful application, and thusdemands the use of heated humidification, nasal decongestants andsteroids as well as intensive support with regular follow-up to improveCPAP adherence. Besides compliance, the CPAP apparatus presents localproblems such as bloating, nasal drying, dry eyes and itchiness offacial skin. In addition, bed partners are adversely affected. CPAP isalso dependent upon electrical power making it difficult to use whiletravelling. As a result, CPAP compliance is only about 40%. Also, thehigh cost of CPAP delivery makes it a problem in third world countriesand the routine use of such devices is difficult to justify.

Surgical treatments have also been advocated for the treatment of OSA.The most common surgical procedure for OSA is uvulopalatopharyngoplasty(UPPP) in which the uvula and redundant soft tissue of the soft palateis resected. The long term success of UPPP is only 20% after 2 years.Only about 41% of patients who undergo the procedure obtain an AHI offewer than 20 events per hour. In addition, 20 events per hour is notalways judged an adequate surgical outcome, especially in view of theuncertain correlation between AHI and apnoea complications. In manycases, snoring will stop after UPPP, but disordered breathing continues,leading to silent apnoea. Thus, the role of UPPP without tongue baseadvancement surgery for treatment of OSA is rather limited.

Radiofrequency (RF) treatment of the tongue base produced promisingearly results but was not consistent in the long term. Newer surgicalapproaches, such as laser-assisted palatal procedures and radiofrequencyablation techniques, have also been disappointing.

Surgical implants have also been used to treat OSA. The AIRvance systemmade by Medtronic uses a titanium screw that is inserted into theposterior aspect of the mandible at the floor of the mouth. A loop ofsuture is passed through the base of the tongue and attached to thescrew. This procedure provides a hammock or suspension for the tongue,making it less likely for the base of the tongue to collapse duringsleep. However, during wakefulness, the suture material acts as acutting device and migrates anteriorly losing its efficacy within a fewmonths.

Another tongue suspension device known as the Repose™ also has onlylimited efficacy. This device also utilises the suture and screwconcept. However, the gains appear to be only short term and its longterm prognosis as a tongue suspension device is poor.

US2008/066769A1 (Dineen) also discloses a flexible elongate elementwhich is secured between the mandible and the base of the tongue. Atensioner is provided by Dineen which assists in adjusting the tensionin the elongate element after implantation. This device is complex andconsidered to have the same limitation as those of the AIRvance andRepose™ devices. Dineen discloses coating the elongate element with abioabsorbable coating which may cause scar or connective tissueformation about the elongate element and which is thought may helptightening the tongue tissue to resist migration of the implant. Theconnective tissue is intended to be formed at the base of the tongueonly. It is aimed at preventing muscle tearing or damage caused by theimplant of barbs or hooks. However, any scar or connective tissue formedon the coating about the elongate element will at best form a sheathover the elongate element and its movement will of course be limited tothat of the elongate element. Furthermore, the device disclosed inDineen is mostly non-absorbable and consequently may be more prone toinfection which may limit its clinical application.

While tongue advancement offers a useful method of treating OSA, thereis currently no practical, long term method of achieving this.

SUMMARY OF THE INVENTION

In accordance with this invention there is provided an implantabledevice for aiding in generating connective tissue between a pair ofanatomical structures in a mammalian body including

an elongate, flexible tether which can be secured between the anatomicalstructures and which carries a scaffold which is generally porous so asto be capable of promoting tissue ingrowth and collagen deposition alongits length, the scaffold extending along the tether for a sufficientdistance so that it is securable in at least close proximity to ananatomical structure at either end, and wherein the length of the tetheris selected to be a desirable maximum distance between the anatomicalstructures along a desired path when secured therebetween, characterisedin that the pores extend through the scaffold and each have a diameterin the range of about 10 μm to about 200 μm.

Further features of the invention provide for the pores to extendthrough the scaffold; each pore to have a diameter of about 50 μm to 180μm, more preferably 100 μm to 150 μm, most preferably about 150 μm; forthe scaffold to be sleeve-like and to extend over the tether; for thescaffold to be tubular; for the scaffold to be made from a polymericmaterial and to be formed by a moulding, casting or meltblending/extrusion process, with or without the addition and extractionof porogens; and for the scaffold to be made from micro- or nanofibers.

Yet a further feature of the invention provides for the scaffold to becapable of at least some elastic elongation.

Still further features of the invention provide for the scaffold to bemanufactured from a stable or non-degradable material; for the stable ornon-degradable material to be a thermoplastic elastomer; for thethermoplastic elastomer to be selected from: polyurethanes such asPellethane™, Estane™, Texin™, elastane and CarboSil™; polyurethane ureassuch as Biomer™, Biospan™, Mitrathane™ and Lycra™; carbonate containingpolyurethanes such as Chronoflex™ and Bionate™; polydimethylsiloxanecontaining polyurethanes or polyurethane ureas such as Pursil™,Elast-Eon™ and Cardiothane™; polyurethanes containing both carbonate andpolydimethylsiloxane moieties; polyurethanes containing soft segmentssuch as hydrocarbons or dimerol and/or partial crosslinking for improvedchemical stability and mechanical properties; silicone, Silastic™,Silupran™, styrene, (co)polyester, polyolefin, polydiene and polyvinylchloride based synthetic elastomers; or a natural rubber; for theelastomer to preferably be CarboSil™ or one of the polyurethane ureas.

Alternatively, for the scaffold to be manufactured from an absorbablematerial; for the absorbable material to be selected from polylacticacid, polyglycolic acid, polycaprolactone, polydioxanone,polyhydroxybuterate, polyiminocarbonates, polysebacic acid, degradablepolyurethanes such as DegraPol™ and copolymers thereof.

Yet further features of the invention provide for the tether to beabsorbable; for the tether to be provided by a plurality of filaments;for the filaments to be made from suture material; and for the filamentsto be welded, woven or braided together along part of their length.

Still further features of the invention provide for each end of tetherto be securable to an anatomical structure through one or more loops inthe tether, or a suturing needle secured to the end of each filament, ora combination of these; for the or each loop to be shaped to receive afixation screw; for the one or more loops to be equally spaced along thelength of the tether; and for the loops to be spaced approximately 10 mmapart.

According to one aspect of the invention the device is configured toprovide support for a tongue base, the scaffold being selected to bebetween 50 mm and 100 mm long, preferably about 70 mm long; for thescaffold to be about 0.5 mm thick and have an internal diameter of about2 mm and for the tether to be made from two or more, preferably four,filaments, and wherein the filaments are shaped to provide one or moreloops at one end and each have a suturing needle secured to the oppositeend.

Further features according to this aspect provide for the one or eachloop to be shaped to receive bone fixation screw; for there to be threeloops spaced along the length of the tether, preferably spaced apart byabout 10 mm.

The invention also provides an implantable device which is suitable foraiding in generating connective tissue between the base of a tongue anda chin in a mammalian body and shaped to be securable at its endsbetween the base of a tongue and a chin, the device including anelongate and flexible tether with a tensile strength sufficient toadvance the base of the tongue towards the chin and maintain it in suchposition, and characterised in that the tether is made of an absorbablematerial and in that a sleeve-like scaffold which is generally porous soas to be capable of promoting tissue ingrowth and collagen depositionalong its length is provided over the tether, the scaffold extendingalong the tether for a sufficient distance so that it is securable in atleast close proximity to the base of the tongue and chin at either end.

Further features of the invention provide for the scaffold to be madefrom a polymeric material and for the pores to extend through thescaffold and each have a diameter in the range of about 10 μm to 200 μm,preferably about 50 μm to 180 μm, more preferably 100 μm to 150 μm, mostpreferably about 150 μm.

Still further features of the invention provide for the tether to beprovided by a plurality of filaments; for the filaments to be made ofsuture material; for the filaments to be shaped to provide one or moreloops at one end of the tether; for a suturing needle to be secured toeach filament at the opposite end of the tether; and for the or eachloop to be shaped to receive fixation screws.

Still further features of the invention provide for the one or moreloops to be equally spaced along the length of the tether; and for theloops to be spaced approximately 10 mm.

Yet further features of the invention provide for the scaffold to bebetween 50 mm and 100 mm long; for the scaffold to be about 0.5 mmthick; and for the scaffold to have an internal diameter of about 2 mm.

The invention also provides a method of generating connective tissue ina mammalian body which includes creating an incision in the body andsecuring between a pair of anatomical structures which are movablerelative to each other an elongate, flexible tether carrying a scaffoldsuch that the length of the tether is a desirable maximum distancebetween the anatomical structures along a desired path and wherein thescaffold is elongate and generally porous so as to be capable ofpromoting tissue ingrowth and collagen deposition along its length andsecured such that it is in at least close proximity to the anatomicalstructures at either end and permitting tissue ingrowth and collagendeposition in and on the scaffold over a period of time.

A further feature of the invention provides for the pores to extendthrough the scaffold and each have a diameter in the range of about 10μm to 200 μm, preferably about 50 μm to 180 μm, more preferably about100 μm to 150 μm, alternatively about 125 μm to 180 μm, most preferablyabout 150 μm.

Further features of the invention provide for the tether to be made of amaterial which is absorbed into the body over a period of time; and forthe scaffold to be made of a material which is stable and non-degradableor of a material that is absorbable and absorbed into the body over aperiod of time.

Still further features of the invention provide for the scaffold to becarried as a sleeve over the tether; and for the sleeve to be about 0.5mm thick and have an internal diameter of about 2 mm.

The invention still further provides a method of providing a support fora tongue base which includes causing connective tissue to be generatedbetween the base of the tongue and the chin by securing between the baseof the tongue and the chin an elongate, flexible tether carrying anelongate sleeve-like scaffold which is generally porous so as to becapable of promoting tissue ingrowth and collagen deposition along itslength, advancing the base of the tongue towards the chin a desireddistance using the tether, and permitting a tendon to be formed betweenthe chin and tongue in and on the scaffold.

Further features of the invention provide for the tether to be made ofan absorbable material and for the method to include the steps ofstitching the device to the base of the tongue; and for providing one ormore holes and screws for screwing the device into the chin.

The invention still further provides a method of treating sleep apnoeawhich includes securing between the base of the tongue and the chin anelongate, flexible tether carrying an elongate scaffold which isgenerally porous so as to be capable of promoting tissue ingrowth andcollagen deposition along its length, advancing the base of the tonguetowards the chin a desired distance using the tether, and permitting atendon to be formed between the chin and tongue in and on the scaffold.

An embodiment of the invention will now be described, by way of exampleonly, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a three-dimensional view of an implantable device for aidingin generating connective tissue in accordance with the invention;

FIG. 2 is a cross-section of the implantable device of FIG. 1;

FIG. 3 is a schematic illustration showing tethers stacked in a weldingnest prior to being contacted with an ultrasonic horn for ultrasonicwelding of the tethers;

FIG. 4 is a schematic illustration showing how the tethers are bondedtogether when the ultrasonic horn is brought into contact with thewelding nest;

FIG. 5 is a cross-section of a human head showing anatomical structures;

FIG. 6 is cross-section of a human head showing anatomical structureswith arrows indicating the direction airflow into the trachea;

FIG. 7 is cross-section of a human head showing the anatomicalstructures when certain structures collapse to block airflow into thetrachea;

FIGS. 8 to 17 are illustrations of the steps for implanting theimplantable device into the tongue and chin; and

FIG. 18 is a bar graph showing the results of stress strain testscarried out on scaffolds made of polydioxanone and polyurethane (PDO+PU)and tether filaments made of polydioxanone (PDO), a polyurethanescaffold alone (PU), polydioxanone filaments alone (PDO) and apolypropylene device (PP) that were explanted from sheep after 8, 16 and32 weeks respectively.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

An implantable device is provided which may be used to aid in generatingconnective tissue between a pair of anatomical structures in a mammalianbody. The connective tissue is formed by collagen and other tissues anddepending on the nature of the anatomical structures the connectivetissue may be termed a tendon or a ligament. A tendon extends between amuscle and a bone while a ligament extends between bones or cartilagesat a joint or supporting an organ.

It is anticipated that the device will typically be used to aid ingenerating connective tissue between anatomical structures which aremovable relative to each other but it could be employed where thestructures are generally stationary relative to each other.

The device includes an elongate, flexible tether which can be securedbetween the anatomical structures and which carries a scaffold. Thelength of the tether is selected to be a desirable maximum distancebetween the anatomical structures along a desired path when securedbetween tethers. For movable structures this distance would be theapproximate desired distance when the structures are fully flexed orextended or moved away from each other. For stationary structures thedistance would be the approximate desired distance the structures shouldbe apart from each other.

The tether may also be selected to be capable of elastic elongation forcertain applications. Where the tether is capable of elastic elongationits length may be selected to be a desirable maximum distance betweenthe anatomical structures along a desired path when secured betweentethers and when in an elastically elongated condition. This may assistin ensuring that a certain degree of slack in the tether is avoided,possibly completely avoided, when the anatomical structures are aminimum distance apart.

The tether is also selected to provide a desired amount of tensilestrength which is generally the amount of strength required to overcomeforces of separation exerted between the anatomical structures. Thisensures that the structures do not move more than the desired distanceapart from each other. Depending on the anatomical structures and thetypical forces exerted between them the tether may be required to have atensile strength of between 10 N and 1000 N.

Typically the tether can be made from suture material, but any suitablebiocompatible material could be used. In this specification, the term“suture material” shall have its widest meaning and include anybiocompatible material from which an elongate thread with sufficienttensile strength to provide mechanical support to anatomical structurescan be formed. Suture materials can be natural or synthetic, absorbableor non-absorbable and can have a range of different characteristics suchas being pliable, elastic or flexible. The term “absorbable” as usedherein shall have its widest meaning and generally refers to the abilityof a material to be degraded in the body so as to lose its structuralintegrity over time. Alternative terms that may be used to describe thischaracteristic of a material include degradable, reservable andbioresorbable.

Commonly used suture material offers the advantage of being readilyavailable and its properties well understood. The tethers can be made ofabsorbable suture materials such as polylactic acid, polyglycolic acid,polycaprolactone, copolymers of the aforementioned, polydioxanone(PDO/PDS), polyhydroxybuterate, polyiminocarbonates, polysebacic acidcopolymers, copolymers of lactide and glycolide such as polyglactin(Vicryl™), homo polymers of glycolide such as Dexon™ (polyglyconicacid), polyglyconate (Maxon™) or poliglecaprone (Monocryl™). The tethersare preferably made of polydioxanone (PDO) or polyglactin (Vicryl™)which have the required long term strength whilst also beingbiodegradable. Polydioxone (PDO) has been found to work well and it isdegraded within the body over a period of time through the process ofhydrolysis.

Alternatively, the tethers can be made of non-degradable or stablematerials such as polyethylene, ultra-high molecular weightpolyethylene, polypropylene, polyamides (Kevlar™) nylons, polyesters, orother high strength fibre forming polymers. In the event thatnon-degradable tethers form part of the device, it is foreseen that thetethers may be removed a certain period of time after implantation ofthe device and following the generation of connective tissue between theanatomical structures. If the tether is to be removed it will preferablybe configured so that it can be removed with the least amount ofdifficulty or damage to the surrounding tissue. Thus, the tether may,for example, be formed with a generally uniform, smooth surface tofacilitate it being pulled or withdrawn from surrounding connectivetissue.

The tether may be provided by a number of filaments, each of which canbe provided by suture material, and the filaments can also be worked tohave a desired tensile strength. For example the filaments can befolded, braided or woven into a suitably strong configuration. They canalso be bonded together, for example by ultrasonic welding, compressionthermal welding, RF welding or shrink tube welding, or alternatively maybe bonded together using chemical, solvent or adhesive based techniques.

The tether could also be made from a suitable material to have a desiredthickness or cross-sectional profile, and could have grooves or channelsin its surface if desired. The tether need not be solid but may have abraided, twisted or otherwise non-uniform surface and may also be porousor so as to permit the migration of cells into the tether structure.

The tether can be secured in position by any suitable means depending onthe nature of the anatomical structures. Where secured to muscle itcould be passed through the muscle and knotted in position.Conveniently, a suturing needle may be secured to the end of the tetheror each filament making up the tether to assist in passing it throughthe muscle and knotting it in position. Where secured to bone it couldbe secured to a screw placed in the bone. If secured between two bonesor bony structures it could be secured by a screw at each end. Thescrews can conveniently extend through loops formed in the tether. Whereit is secured to a screw or similar device placed in bone it isdesirable that the screw also be a made from an absorbable material. Oneexample of such material is Lactosorb™ (Biomet).

The tether defines a path for growth of connective tissue which isinitiated by cellular migration into the scaffold. The porous scaffoldis selected to permit and encourage the ingrowth of fibrovascular tissuefrom surrounding tissue along its length. Cellular migration refers tothe migration of cells such as fibroblasts and myofibroblasts into thepores of the scaffold. These cells deposit extracellular matrix,including collagen in and on the scaffold and eventually connectivetissue is generated. The scaffold is provided by a porous body,preferably a membrane, in which the pores each have a diameter in therange of about 10 μm to 200 μm, preferably about 50 μm to 180 μm, morepreferably 100 μm to 150 μm, most preferably about 150 μm. A 10% to 15%coefficient of variation (CV) is typically expected for the pore sizes.The pores need not have a uniform diameter but it is desirable in thecase of non-uniform diameters that the minimum and maximum diametersfall within these ranges. The pores extend through the body to permitfibrovascular material to propagate through the scaffold. As the poresextend from one side to the other of the scaffold material fibrovascularmaterial is able to propagate from the outside of the scaffold throughto the inside of the scaffold which abuts or is in proximity with thetether. This culminates in the deposition of collagen and subsequentlyorderly connective tissue is established and propagated on both sides ofthe body of the scaffold.

The scaffold is made from a biocompatible material, preferably athermoplastic elastomer such as a polyurethane, even more preferablyCarboSil™ with a hardness (Durometer hardness Shore A) of 80A.

Other suitable elastomeric materials that the scaffold may be made ofwhich are stable, i.e. non-degradable, include polyurethanes such asPellethane™, Estane™, Texin™ and elastane; polyurethane ureas such asBiomer™, Biospan™, Mitrathane™ and Lycra™; carbonate containingpolyurethanes such as Chronoflex™ and Bionate™; polydimethylsiloxanecontaining polyurethanes or polyurethane ureas such as Pursil™,Elast-Eon™ and Cardiothane™; polyurethanes containing both carbonate andpolydimethylsiloxane moieties; polyurethanes containing soft segmentssuch as hydrocarbons or dimerol and/or partial crosslinking for improvedchemical stability and mechanical properties; silicone, Silastic™,Silupran™, styrene, (co)polyester, polyolefin, polydiene and polyvinylchloride based synthetic elastomers; or a natural rubber.

Alternatively, the material could be an absorbable material that isabsorbed into the body over a period of time such as polylactic acid,polyglycolic acid, or polycaprolactone, copolymers of the threeaforementioned materials, polydioxanone, polyhydroxybuterate,polyiminocarbonates, polysebacic acid copolymers, and degradablepolyurethanes, such as DegraPol™.

Any suitable method of making the scaffold can be used. For example itcould be made by a moulding, casting or melt blending/extrusion process,with or without the addition and extraction of porogens. Porogens areparticles of a specified shape and size that are used to make pores instructures made by any one or more of the above processes. The porogensare usually dissolved away after the material has set thereby providinga microporous material. While porogens often take the shape of beadsthey could also be provided by nano- or microfibers which can bedissolved or otherwise removed from the structure to provide pores.Further alternative methods of making the scaffold involve the use ofmicro- or nanofibers which form a porous mat or pile, such as byspinning onto a flat surface, or which are formed into a thread and thenwoven or knitted or braided into a suitable shape, or by directlyspinning tubular structures onto a rotating mandrel using the process ofelectrospinning.

Where spherical porogens are used to create the pores these can be sizedused appropriate sieves. Typical sieves may be in the ranges 30-45 μm,53-63 μm, 63-75 μm, 90-106 μm and 150-180 μm, each with an approximateCV of 10% to 15%.

The material used for the scaffold may be made in the form of a membranewhich may have a thickness of less than 2 mm, preferably less than 1 mm,most preferably about 0.5 mm.

The scaffold can be carried on the tether in any suitable fashion.Conveniently it could have a tubular shape which extends over the tetheras a sleeve or in a sleeve-like manner. The tubular scaffold may beformed from a single tubular member or a series of rings or squat tubesthat are stacked or attached to one another to form an elongate tubularstructure.

The internal diameter or circumference of the scaffold should becomplementary to, or approximate, the outer diameter or circumference ofthe tether. It is not necessary for the scaffold to provide a very tightfit over the tether although it should not be too loose either. It isdesirable that a contiguous, or lightly touching, fit be provided. Whenthe scaffold lightly touches the tether it allows some space to existbetween the tether and scaffold to permit collagen deposition betweenthe two. With the scaffold contiguous with the tether about itscircumference cells are thus still able to migrate between the scaffoldand tether. Where the tether is made of a number of strands or filamentsof suture material it typically has a non-uniform external surface. Ascaffold carried as a sleeve over such a tether may provide a stretchfit and leave sufficient space due to the non-uniform surface. Also, asthe tether absorbs into the body, collagen and other tissue fills theentire space left by it.

The scaffold should be flexible. It should preferably also be capable ofat least some elastic elongation particularly where the tether iscapable of elastic elongation. Where the tether is not capable ofsignificant elastic elongation this property is not strictly required ofthe scaffold.

The scaffold is preferably elongate and continuous but it will beunderstood that small gaps could be provided in its length or porositywhich will be spanned by fibrovascular material. The length of thescaffold will typically approximate that of the tether between theanatomical structures so that the scaffold is held in close proximity,or abutting, the anatomical surfaces.

The scaffold need not have a tubular shape and could be shaped topartially cover the tether or be integrated into the tether, such as byweaving, braiding, making a yarn. Thus, for example, yarns of a suitablescaffold material could be twisted or woven together with the suturematerial of the tether.

While it is desirable to secure the ends of the scaffold abutting or inclose proximity to the anatomical structures, it is not critical thatthis be done. Heterotopic bone formation will typically ensure that bonegrows out and joins the collagen within and on the scaffold creating atruly biological attachment.

It is also desirable that movement of the device occur as thisstimulates the growth and alignment of collagen. Importantly, it alsostops ossification or the formation of bone from the tissue.

The cross-sectional shape of the device is generally dependant on theapplication and the type of connective tissue it is desired to generate.In many instances the tether and scaffold will have a generally round orcircular cross-section but it is envisaged that a flattened, oval orstrap-like profile could be used for approximating that of, for example,ligaments of long bones. This can be fairly easily achieved by, forexample, braiding suture material into a strap-like configuration andsliding a complementary sleeve of scaffold material thereover in asheath-like fashion.

In one application, an implantable device is provided that is suitablefor aiding in generating connecting tissue between the base of a tongueand a chin in a mammalian body. The device is shaped to be securable atits ends between the base of the tongue and the chin. The deviceincludes an elongate and flexible tether which has sufficient tensilestrength along a length thereof to advance the base of the tonguetowards to chin and maintain it in such position. A tensile strengthrequired by the tongue to prevent it falling back against the throat mayrange between 10 N and 100 N, but is typically 30 N. The tether musttherefore have a tensile strength that is at least 10 N, preferably atleast 30 N. A tether with a tensile strength of between 10 N and 100 Nshould be sufficient. A generally porous scaffold is provided on thetether. The scaffold extends along the tether for a sufficient distanceso that it is securable in close proximity to the base of the tongue andthe chin to enable connective tissue to be generated between the base ofthe tongue and the chin. The implantable device which is configured toaid in generating connecting tissue between the base of a tongue and achin is suitable for treating conditions related to sleep apnoea inhumans.

One embodiment of an implantable device (1) is shown in FIGS. 1 and 2and includes an elongate, flexible tether (3) which carries a scaffold(5). The tether (3) is provided by two round filaments (7) of suturematerial, in this embodiment polydioxanone (PDO) having a diametergrading of 0,0 USP, which are folded about themselves to provide firstend (9), at which the filaments (7) are bent, and a second end (11) atwhich the ends (13) of the filaments (7) are loose.

A half-circle tapered needle (15) is attached to the end (13) of eachfilament (7). This may conveniently be achieved by crimping inconventional fashion.

Three loops (17, 19, 21) or eyelets are provided spaced apart from eachother at the first end (9). The first loop (17) is provided at the end(9). The second loop (19) is spaced 10 mm from the first loop (17) andthe third loop (21) spaced 10 mm from the second loop (19). Each loop(17, 19,21) has an internal diameter of 2 mm in this embodiment.

The loops (17, 19, 21) are formed by bonding the filaments (7) togetherbetween the first loop (17) and second loop (19), the second loop (19)and third loop (21) and for about 10 mm after the third loop (21). Inthis embodiment the filaments (7) are bonded together using ultrasonicwelding which may be achieved as follows. Referring to FIGS. 3 and 4,the four filaments (7) are placed within a welding nest (30) or anvilstacked one on top of the other. An ultrasonic horn (32) is then broughtinto contact with the welding nest (30) and used to apply vibrationalenergy to the stacked filaments (7). The abutting edges of the filamentsserve as energy directors and the vibrational energy is transformed intofrictional thermal energy which produces a localized weld withoutsignificant damage to the filaments (7).

Other bonding methods can be energy based or chemical, mechanical,solvent or adhesive based. For example, the filaments (7) could besubjected to other forms of welding energy including compression thermalwelding with heated dies, RF welding to provide very local welding atthe interface of the two fibers or shrink tube lap welding. While thefirst three methods of welding provide welded joints, the use of theshrink tube welding may be preferable as it produces a solid, seamlesswelded region.

Shrink tube welding uses a shrink tube that has a transition temperature(shrink temperature) that is greater than the melt temperature of thePDO filaments. Thus, as the shrink tube collapses or compresses at thetransition temperature and exerts a compaction force on the filaments,the molten filament polymer flows together and effectively welds. Theshrink tube is subsequently removed leaving the filaments in a weldedstate. Additionally, the shape of the welded zone may be adapted topreferred geometries of the loops (17, 19, 21) by a non-uniform shrinktube or by confinement of the shrink tube by horizontal compression.

Referring again to FIGS. 1 and 2, the scaffold (5) is, in thisembodiment, provided by a membrane having a thickness of about 0.5 mmand which is tubular in shape with a length of about 70 mm and aninternal diameter of about 2 mm. Importantly, the scaffold (5) is porouswith the pores each having a diameter of about 125 μm to 180 μm and eachextending through the membrane. In this embodiment the scaffold is madefrom a biocompatible polyurethane material called CarboSil′ from DSM.

The scaffold (5) is flexible and extends over the tether (3) in asleeve-like manner. Conveniently, it can be inserted over the second end(11) of the tether (3) before the needles (15) are secured to thefilaments (7). It provides a fairly loose fit over the tether (3) andspace is thus provided between the filaments (7) and between thefilaments and the scaffold (5). The scaffold (5) extends along thetether (3) for a sufficient distance so that it is securable in closeproximity to the base of the tongue and the chin. The scaffold (5)serves as a platform for the growth of connective tissue and the growthand strengthening of the connective tissue is stimulated by thefunctioning and movement of the tongue as described in more detailabove.

The scaffold (5) does not absorb in vivo, in this embodiment, but actsas a platform for the ingrowth of fibro-collagenous material. Itstensile strength is essentially increased with the deposition of orderlycollagen fibers. The filaments (7) are absorbable in vivo and undergodegradation and absorption through hydrolysis over a period of 24 weeks.The filaments (7) are therefore expected to totally absorb within aperiod of 24 weeks, leaving the scaffold (5) filled withfibro-collagenous material, further strengthened by the tensile forcesproduced by physiological functioning of the intrinsic muscle.

The device (1) is suitable for aiding in generating connecting tissuespecifically between the base of a tongue and a chin in a mammalianbody. Such a device is shaped to be securable at its ends (9, 11)between the base of the tongue and the chin. The device includes anelongate and flexible tether (3) which has sufficient tensile strengthalong a length thereof to advance the base of the tongue towards to chinand maintain it in such position. A tensile strength required by thetongue to prevent it falling back against the throat may range between10 N and 100 N, but is typically 30 N. The tether must therefore have atensile strength that is at least 10 N, preferably at least 30 N. Atether with a tensile strength of between 10 N and 100 N may besuitable.

Prior to describing the device (1) in use, the anatomy relevant to itsuse between the base of a tongue and a chin will be described. FIG. 5shows a cross-section of a human head with anatomical structuresincluding the nasal cavity N, bone B of the hard palate HP, the softpalate SP, the mouth M, the tongue T, the trachea TR, the epiglottis EP,the esophagus ES, and the posterior pharyngeal wall PPW. In the humanhead, an air filled space between the nasal cavity N and the larynx LXis referred to as the upper airway.

The most critical part of the upper airway associated with sleepdisorders is the pharynx PX. Referring to FIG. 6, the pharynx has threedifferent anatomical levels. The nasopharynx NP is the upper portion ofthe pharynx located in the back of the nasal cavity N. The oropharynx OPis the intermediate portion of the pharynx containing the soft palateSP, the epiglottis EP, and the curve at the back of the tongue T. Thehypopharynx HP is the lower portion of the pharynx located below thesoft tissue of the oropharynx OP. The oropharynx OP is the section ofthe pharynx that is most likely to collapse due to the high prevalenceof soft tissue structure, which leaves less space for airflow. Thehypopharynx HP lies below the aperture of the larynx and behind thelarynx, and extends to the esophagus.

The soft palate and the tongue are both flexible structures. The softpalate SP provides a barrier between the nasal cavity N and the mouth.In many instances, the soft palate SP is longer than necessary andextends a significant distance between the back of the tongue T and theposterior pharyngeal wall PPW.

Although the muscles relax throughout the body during sleep, most of themuscles of respiratory system remain active. During inhalation, thediaphragm contracts and causes negative pressure to draw air A into thenasal cavity N and the mouth M. The air then flows past the pharynx PX,through the trachea TR and into the lungs. The negative pressure causesthe tissue of the upper airway to deform slightly, which narrows theairway AW passage. In apnoeic patients, the soft palate SP, the tongueT, and/or the epiglottis EP collapse against the posterior pharyngealwall PPW to block airflow into the trachea, as shown in FIG. 7. As theairway AW narrows, airflow through the pharynx becomes turbulent whichcauses the soft palate SP to vibrate, generating a sound commonly knownas snoring.

During sleep, humans typically experience brief obstructions of airflowand/or small decreases in the amount of airflow into the trachea andlungs. An obstruction of airflow for more than ten seconds is referredto as apnoea. A decrease in airflow by more than fifty percent isreferred to as hypopnoea. The severity of sleep disorders is measured bythe number of apnoeas and hypopnoeas that occur during every hour ofsleep.

If apnoea or hypopnoea occurs more than five times per hour, mostmedical personnel diagnose the individual as having an upper airwayresistance problem. Many of these patients often exhibit symptomsrelated to sleep disorders including sleepiness during the day,depression, and difficulty concentrating. Individuals having ten or moreepisodes of apnoea or hypopnoea during every hour of sleep areofficially classified as having obstructive sleep apnea syndrome (OSAS).As the airway AW is obstructed, the individual makes repeated attemptsto force inhalation. Many of these episodes are silent and arecharacterized by movements of the abdomen and chest wall as theindividual strains to draw air into the lungs. Typically, episodes ofapnoea may last a minute or more. During this time, oxygen levels in theblood will decrease. Ultimately, the obstruction may be overcome by theindividual generating a loud snore or awakening with a choking feeling.

Referring to FIG. 6, when an individual is awake, the back of the tongueT and the soft palate SP maintain their shape and tone due to theirrespective internal muscles. As a result, the airway AW through thepharynx remains open and unobstructed. During sleep, however, the muscletone decreases and the posterior surface of the tongue and the softpalate become more flexible and distensible.

Referring to FIG. 7, without normal muscle tone to keep their shape andanatomical position either alone or as a group, the posterior surface ofthe tongue T, the epiglottis EP, and the soft palate SP tend to easilycollapse to block the airway AW.

The use of the implantable device (1) in the treatment of apnoea willnow be described with reference to FIGS. 8 to 17 which illustrate thesteps of implanting the device. The treatment includes providing asupport for a tongue base by causing connective tissue to be generatedbetween the base of the tongue and the chin by securing between the baseof the tongue and the chin an elongate, flexible tether carrying anelongate scaffold which is generally porous so as to be capable ofpromoting tissue ingrowth and collagen deposition along its length,advancing the base of the tongue towards the chin a desired distanceusing the tether and permitting a tendon to be formed between the chinand tongue in and on the scaffold. After or during formation of thetendon the tether can be removed or be permitted to be absorbed into thebody.

If the scaffold is tubular so as to be in the form of a sleeve, theformation of tendon on the scaffold includes tendon forming around andwithin the sleeve through cellular migration and connective tissuegrowth as discussed above. Such cellular migration and connective tissuegrowth also takes place in the pores of the scaffold. The scaffold neednot have a tubular shape and could be shaped to partially cover thetether or be integrated into the tether, in which case the tendon formson and around portions of the scaffold as well as in the pores of thescaffold.

Initially the lower lip (51) is retracted and a vestibular incision (53)is carried out to incise the mucosa and Mentalis muscle of the chin asshown in FIG. 8. The Mentalis muscle is then stripped to expose the bonyprominence (55) of the chin as shown in FIG. 9. A fenestration (57) orwindow is then formed in the prominence (55) of the chin at a sub-apicallevel of the lower incisor teeth (59) as shown in FIGS. 10 and 11. Thefenestration is created by an osteotomy of both the outer and innercortices of the bone. A 701 bur is used to make the perforation in thebone which is then removed through an osteotome. It is recommended toremove each cortex separately.

Access to the floor of the mouth is thus achieved. Alternatively, a bonetrephine measuring 10 mm in diameter may also be used to create thefenestration access. FIG. 11 illustrates the bicortical fenestration(57) to the floor of the mouth as seen from a lateral perspective. It iswithin this fenestration bony defect that a fixation screw will beplaced in order to provide anchorage to the implantable device.

A second incision (61) is made on the dorsal aspect of the tongue (63)just anterior to the V-shape depicted by the circumvallate papillae (65)as shown in FIG. 12. Sharp dissection is carried through to the tonguebase while the wound is retracted laterally using traction sutures (67).Referring to FIGS. 13 to 15, two anchorage sutures (50) are inserteddeep into the intrinsic muscle of the tongue (63), one being anteriorand the other posterior, using the needles (15) and filaments (7) at theend (13) of the device (1) shown in FIGS. 1 and 2. After the needles(15) have been removed and discarded, the sutures (50) are tensioned andtied together so that the two on the right side make a single knot (70)and the same is done for the two on the left side. In this way, the end(52) of the scaffold (5) is well embedded into the base of the tongue(63) as shown in FIG. 15. The knotted end of the device (1) isillustrated in the deep aspect of the tongue muscle before the pushthrough into the floor of the mouth. By pulling anteriorly on the device(1) the validity and strength of the attachment to the tongue base istested clinically.

The device (1) is soaked in a solution of 200 ml of saline mixed withGentamycin™ (Fresenius 80 mg/2 ml vials) for at least 30 minutes beforeinsertion. This precaution is to prevent infection of the device (1) andparticularly the porous scaffold (5). Also, a non-touch technique,preferably avoiding contact with the facial skin should be employed.

Once the validity and strength of the attachment is shown to besatisfactory, the push through/pull through method is employed. Acurved, blunt artery forceps is used to engage one of the loops (17, 19,21) and carry the first end (9) of the device (1) through the floor ofthe mouth towards the fenestration in the chin (FIG. 16). The first end(9) of the device (1) is then engaged through the chin fenestration andpulled through gently. The base of the tongue is then advanced towardsthe chin a desired distance using the tether. Advancing the base of thetongue about 10 mm is typically sufficient and is often denoted by adepression in the base of the tongue. The 10 mm spacing of the loops(17, 19, 21) simplifies the distance estimation when the tongue needs tobe advanced by 10 mm.

A 9 mm by 2.0 mm hole (71) is drilled into the medulla of the chinwithin the fenestration window (57) and the same size Lactosorb™ screw(73) is secured in the hole (71) after being fed through an appropriateloop (17, 19, 21) in the tether (3), as shown in FIG. 17.

The bone that is removed is not replaced as new bone will eventuallyfill into the gap. The Lactosorb™ screw is absorbable and degrades veryslowly through hydrolysis after 32 weeks and is only completely absorbedafter 52 weeks. Its initial strength within the first 32 weeks more orless equals that of titanium.

The wound on the dorsum of the tongue is closed using a USP 3-0polyglycolic acid suture and the wound in the lip is closed with USP 5-0polyglycolic acid suture.

As shown in FIG. 17, in its final implanted position the device (1)provides a tongue support which not only supports the tongue base fromfalling against the posterior pharyngeal wall during sleep, but alsoadvances the tongue base so that the compliance of the oro- andhypopharynx is improved and secured, thereby making obstruction of thelower airway AW impossible.

While the check is initially provided by the tether (3), during the timein which it takes for the PDO of the filaments (7) to be absorbed,tissue ingrowth and collagen deposition within the pores and on thescaffold (5) and between the scaffold (5) and tether (3) occurs. Afterabsorption of the filaments (7) the device forms a naturally inducedbiological tendon which provides the check on the tongue and theprotection that the tongue lacks anatomically. This then avoids theproblems and discomfort associated with migration of the implant throughthe base of the tongue.

At the same time all physiological aspects of tongue muscular function,like speech, swallowing and chewing are not in any way adverselyaffected by the device (1). The scaffold may remain implanted, but isbarely visible as a tendon has developed in and around it. In anembodiment in which the scaffold is degradable over time, it willeventually disappear and only the naturally formed tendon remains.

Thereafter the collagen undergoes maturity. This means that after thedisappearance of the PDO filaments, the scaffold will be overgrown withcollagen bands (including types 1 and 3 confirmed by means ofelectrophoresis) which will not only provide tensile strength to theneo-tendon, but is histologically and biologically attached to theintrinsic tongue muscle of the tongue through the process of orderlyfibrosis, never previously described for inventions of this nature.

The collagen bands strengthen as they are continuously stressed by themovement of the tongue muscle. The movement induces further growth ofthe collagen bands until maturation is achieved. The more stress that isapplied to the collagen bands during movement of the tongue, the morethe collagen grows or accumulates and the stronger the collagen bandsbecome. This characteristic of collagen growth and strengtheningexplains, for example, why the tendon of a thigh is stronger than thatof finger muscles. The tendon of a thigh grows and strengthens as itexperiences more stress in comparison to the tendons in a finger.

Histological studies in sheep have shown that the polyurethane scaffoldsuccessfully induces fibrovascular tissue ingrowth within the first 8weeks post implantation.

Tests were conducted to determine the stress strain behaviour andpossible differences in the ultimate strengths of explanted devicescomprising the device described above (PDO+PU), a polyurethane scaffoldalone (PU), polydioxanone filaments alone (PDO) and a polypropylenedevice (PP) in sheep. The devices were all implanted in sheep in thesame manner as described. The implanted devices were explanted at 8weeks, 16 weeks and 32 weeks respectively.

Explanted samples of week 8 were clamped using Instron grips and pulledat a rate of 5 mm per minute. Three PDO+PU samples and two PDO sampleswere supplied and evaluated. There were distinct differences inappearance in size and shape of the samples, the PDO+PU being muchthicker due to tissue growth. All samples were pulled to break andreasonable data obtained after some difficulties using the directclamping method.

Explanted samples of week 16 could not be successfully clamped using thedirect clamp method because of tissue growth and inability to obtainenough frictional force to overcome the strength of the samples. In anew method Kevlar yarn was used to tie the sample ends to the Instronjaws using knots and hitches.

Two samples of PDO, two of PP and one of PDO+PU were tested. The speedwas increased to 50 mm per min to eliminate the slippage that wasobserved at 5 mm. This method allows for sufficient gripping of theslippery soft tissue to achieve tensile failure.

Thirty two-week explants were tested also using the Kevlar yarn method.Three samples of PDO+PU, two samples of PU, one sample of PDO and onesample of PP were tested. Samples were tensile tested at a speed of 50mm per min and all samples apart from the PP failed in the appropriatemode. In the case of the PP samples, they needed to be cleaned of tissueto get sufficient grip using the Instron clamps to pull to break.

Results are plotted in FIG. 18 and show an increase of strength of thePDO+PU samples with increasing implant time (from 8 to 32 weeks). In thecase of the PDO samples, there is also a general trend of increasingstrength with time, but this is not strictly so, as one of the 16 weekPDO samples was much thicker than the other, resulting in large varianceand increased average ultimate tensile strength. The PP samples remainedat similar strength throughout as expected due to the non-degradabilityof the material.

There is a clear increase in strength for the PDO+PU device with implanttime. The small number of replicates and variation in explant size andshape resulted in a less clear trend with the PDO group.

The present invention is regarded as being superior to all previousimplants (filamentous or metallic structures) in that the implant doesnot eventually rely upon a mechanical or stress interface with theintrinsic muscle of the tongue for adherence or retraction. Instead itpromotes the generation of a tendon which acts as a permanent tonguecheck.

It will be appreciated that many other embodiments of an implantabledevice exist which fall within the scope of the invention, particularlyregarding the shape, configuration and materials used for the tether andthe scaffold. For example the scaffold could be between 50 mm and 100 mmlong and be made from any suitable material. The tether too may be madefrom any suitable number of filaments and could be secured to the chinin any suitable manner.

It will further be appreciated that while the above described device isconfigured for use as a tongue support to assist in the treatment ofapnoea by assisting in the formation of a tendon between the base of thetongue and the chin, the device can be configured to assist in theformation of other types of connective tissue.

Connective tissue in a mammalian body can be generated by creating anincision in the body and securing between a pair of anatomicalstructures which are movable relative to each other, an elongate,flexible tether carrying a scaffold such that the length of the tetheris a desirable maximum distance between the anatomical structures alonga desired path. The scaffold should be elongate and generally porous soas to be capable of promoting tissue ingrowth and collagen depositionalong its length and it should be secured such that it is in at leastclose proximity to the anatomical structures at either end. The incisioncan then be closed and tissue ingrowth and collagen deposition permittedto take place in and on the scaffold over a period of time.

The tether should preferably be made of a material degradable within thebody over a period of time. The scaffold is made of a material that isnot degradable, but it foreseen that it may be desirable for thescaffold to be made of a material which is degradable within the bodyover a period of time.

The manner in which the tether is attached to the anatomical structureswill depend on the nature of the structures and any suitable method canbe used. Similarly, the shape and configuration of the tether andscaffold can be adapted to approximate the natural connective tissue itis desired to generate or to approximate desirable shape of connectivetissue.

The connective tissue generated using the implantable devices of thecurrent invention are truly biological and biologically attached to thebody.

Throughout the specification unless the contents requires otherwise theword ‘comprise’ or variations such as ‘comprises’ or ‘comprising’ willbe understood to imply the inclusion of a stated integer or group ofintegers but not the exclusion of any other integer or group ofintegers.

1. An implantable device for aiding in generating connective tissuebetween a pair of anatomical structures in a mammalian body including anelongate, flexible tether which can be secured between the anatomicalstructures and which carries a scaffold which is generally porous so asto be capable of promoting tissue ingrowth and collagen deposition alongits length, the scaffold extending along the tether for sufficientdistance that it is securable in at least close proximity to ananatomical structure at either end, and wherein the length of the tetheris selected to be a desirable maximum distance between the anatomicalstructures along a desired path when secured therebetween, characterisedin that the pores extend through the scaffold and each have a diameterof about 10 μm to 200 μm.
 2. An implantable device as claimed in claim 1in which the pores each have a diameter of about 100 μm to 150 μm.
 3. Animplantable device as claimed in claim 1 or claim 2 in which thescaffold is sleeve-like and extends over the tether.
 4. An implantabledevice as claimed in claim 3 in which the scaffold is tubular.
 5. Animplantable device as claimed in any one of the preceding claims inwhich the tether is absorbable.
 6. An implantable device as claimed inany one of the preceding claims in which the tether is provided by aplurality of filaments.
 7. An implantable device as claimed in claim 6in which the filaments are made of suture material.
 8. An implantabledevice as claimed in claim 6 or claim 7 in which each end of tether issecurable to an anatomical structure through one or more loops shaped toreceive a fixation screw, or a suturing needle secured to the end ofeach filament, or a combination of these.
 9. An implantable devicesuitable for aiding in generating connective tissue between the base ofa tongue and a chin in a mammalian body and shaped to be securable atits ends between the base of the tongue and the chin, the deviceincluding an elongate and flexible tether with a tensile strengthsufficient to advance the base of the tongue towards the chin andmaintain it in such position, and characterised in that the tether ismade of an absorbable material and in that a sleeve-like scaffold whichis generally porous so as to be capable of promoting tissue ingrowth andcollagen deposition along its length is provided over the tether, thescaffold extending along the tether for a sufficient distance so that itis securable in at least close proximity to the base of the tongue andchin at either end.
 10. An implantable device as claimed in claim 9 inwhich the pores extend through the scaffold and each have a diameter ofabout 10 μm to 200 μm.
 11. An implantable device as claimed in claim 10in which the pores extend through the scaffold and each have a diameterof about 125 μm to 180 μm.
 12. An implantable device as claimed in anyone claims 9 to 11 in which the tether is provided by a plurality offilaments.
 13. An implantable device as claimed in claim 12 in which thefilaments are made of suture material.
 14. An implantable device asclaimed in claim 12 or claim 13 in which a suturing needle is secured toeach filament at one end of the tether and the filaments at the oppositeend shaped to provide one or more loops, the or each loop shaped toreceive a fixation screw.
 15. An implantable device as claimed in anyone of claim 9 to claim 14 in which the scaffold is tubular with aninternal diameter of about 2 mm and a thickness of about 0.5 mm.